Gas-shielded arc-welding method



United States Patent Q 3,258,842 GAS-SHIELDED ARC-WELDING METHOD Sadayoshi Morita, Teiji Ito, and Takeshi- Nishi, Yawata, and Tsuguro Kikuno, Tobata, Japan, assignors to Yawata Iron &- Steel Co., Ltd., Tokyo, Japan, a corporation of Japan No Drawing. Filed Dec. 18, 1962, Ser. No. 245,404 Claims priority, application Japan, Dec. 29, 1961, 36/ 48,065

14 Claims. (Cl. 29-494) This invention relates to a method of arc-welding by using a gas-shielded arc and by which. there is obtained a tough deposited steel. The method involves producing a metallicnit-ride in the deposited steel.

Generally,when carrying out arc-welding in which the arc is. shielded by a shielding gas containing nitrogen, an unfavorable result is produced in that pores will be produced. in thedeposited. metal because of the nitrogen presentin the said shielding gas.

Excess nitrogen in the shielding gas will ordinarily cause the. formation of pores in the deposited metal because it is not able to escape into the atmosphere because the solubility of gases contained in said deposited metal is reduced when said deposited metalcoagulates. However, it has now been found that, when arc-welding is carried out with a gas shield for the arc, that an improved result will be produced by mixing nitrogen in the shielding gas and at the same time adding to .the welding core wire a metallic element which can produce. a nitride. A stable nitride of the said metallic element will be formed in the deposited metal, and the formation of pores will be prevented and a tough deposited metal having no pores will be produced.

It is therefore an object of the present invention to obtain a tough deposited steel having a high notch-toughness and adapted to the nature of the steel material to be welded. during the. arc-welding or" iron and steel materials, and specifically high tensile strength steels and lowtemperature .tough steels having high notch-toughness, by causing the formation of. a nitride in the weld.

One method. of achieving this object of the present invention is to carry out gas-shielded arc-welding of a steel material by using :a welding core wire for welding steel material which contains one or more nitride producing metals or alloys in addition to the ordinary welding core wire composition and a shielding gas to which nitrogen has been added, so that the nitride of the said nitride producing metal will be formed inthe deposited metal.

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gen gas when in a hot state, so that the nitride of the said metal will be produced in the deposited metal. Part of the said metallic nitride can be deposited as a fine solid phase in the deposited metal part during welding or during a subsequent heat-treatment, whereby there is produced a tough deposited metal weld.

As the shielding gas there can be used such inert gases as, for example, argon, helium, a mixture of argon or helium with oxygen or carbon dioxide, carbon dioxide or a mixture of carbon dioxide and oxygen.

As the nitride-producing metals there can be used at least one metal taken from the group consisting of aluminum, titanium, zirconium, beryllium, columbium, vanadiam-and alloys thereof.

Substances which discharge nitrogen when in a hot state can be taken from the group consisting of manganese nitride, calcium nitride, molybdenum nitride and chromium nitride, and such nitrates as Ca(NO) In the arc-welding method of the present invention, any

conventional powdery flux can be used in addition to the said shielding gas so that the weldabi-lity may be further increased.

To the core wire to be used in the present invention can be further added such conventional alloying elements as nickel, molybdenum and chromium to further improve the characteristics of the welded part.

The welding process is carried out in the same manner as the ordinary gas-shielded welding process. However, it is preferable to keep the content of the metallic nitride in the deposited metal substantially within the range of 0.01 to 1.00%. In welding, the nitride-producing metal or alloy contained in the core wire, together with the core wire, will be. melted by the are heat and will form a molten welding bath together with the material being welded, which is melted at the same time. Since dissolved nitrogen from the shielding gas or which is discharged from a nitrogen-discharging substance such as manganese nitride is dissolved in the molten bath, the said nitride producing metal or alloy will form a nit-ride during the coagulation of the bath. Further, under the influence of a subsequent heat-treatment or heat the heat of the molten bath itself, a part of the said nitride will be deposited as a fine solid phase. Thus, the deposited metal will have a fine structure and will have a high toughness.

Examples of the present invention will now be set forth in greater detail. In Examples 1-3, three core wires were used which had the following composition:

Table 1 .Chemical compositions of core wires Part of the said nitride may be deposited as a line solid phase in the deposited metal part during welding or during a subsequent heat-treatment.

Another methodof achieving the object of the present invention is to carry out gas-shielded arc-welding with a shielding gas which need not contain nitrogen but in which there is used a welding core wire containing one or more nitride producing metals and/ or one or more alloys thereof in powdered form and a substance which discharges nitrocomposition of the welds were as shown in Table 2.

Table 2.Chemical compositions of a single layer weld produced with a carbon dioxide-nitrogen shielding gas on low carbon killed steel taining 0.52% titanium, even when up to 12% nitrogen was mixed with the canbon dioxide, no pores were seen to be produced. Thus, it is evident that fixing the nitrogen with a nitride producing element such as aluminum or titanium will be elfe'ctive to prevent the production of pores when nitrogen gas is mixed with the shielding gas.

The steels of the welds having the chemical compositions shown in Table 2, when air-cooled down from 900 C., and a weld produced by using a wire core C but using only a carbon dioxide shielded arc, had the following mechanical proper-ties:

Table 3.-Mechanical properties of single layer welds formed using a carbon dioxide-nitrogen shielded arc Ordinary CO2 shielded arc.

Remarks: 0 represents mechanical properties of single layer weld formed using a wire core 0 but using only-a carbon dioxide shielded arc.

By comparison, when single layer welding steel when using a carbon dioxide-shielded arc and an ordinary lowcarbon silicon-manganese series welding corewire, pores were produced when about 4% nitrogen was mixed with the carbon dioxide shielding gas. However, welding core wire A in Table 1, containing 0.55% aluminum was used, no pores were seen to be produced until 8% of nitrogen was mixed into the shielding gas. Likewise, with an argon gas-shielded arc and a welding core wire containing no aluminum, even with 1% nitrogen in the shielding gas, pores were produced. However, with the welding core wire A in Table 1 containing 0.55% aluminum, no pores were produced until 4% of nitrogen was mixed in the As compared with the weld produced using a carbon A multi-layer weld was made using each of the core wires A, B and C with a carbon dioxide-nitrogen shielded arc. The mechanical properties of the metal of the welds, and the metal of a weld produced with a core wire C and a carbon dioxide shielded arc, were as follows:

Table 4.Mechanical properties 0 a multi-layer weld formed by means of a carbon dioxide-nitrogen shielded Ordinary CO1 shielded arc.

shielding gas. containing titanium, which is higher in its affinity for nitrogen than aluminum, was used, it was possible to increase the amount of nitrogen at which no pores will be produced. For example, in the case of a carbon di- On the other hand, when a core wire The mechanical properties of the steel of the weld are the result of the same welding process was used in Ex-' ample l and heat-treated by the heat of the arc used to form the subsequent layer of the weld. 'Ihissteel possesses excellent mechanical properties because of having oxide-shielded arc, with the core wire B in Table 2 conundergone a normalizing efiect due to the heatofthe layers formed over each other. In such a weld, the mechanical properties of the weld steel formed by an are having no nitrogen mixed in the shielding gas were inferior.

' EXAMPLE 3 uA multi-layer weld was made using each of the core wires A, B and C in Table 1 but using 4% nitrogen in argon for the shielding gas and feeding it at a rate of 25 liters/min. The mechanical properties of the welds were as shown in Table 5, the weld C being formed with a rod C and only argon in the shielding gas. The mechanical properties of these welds were also excellent, as in the above Example 2, and are superior to those of the weld formed with no nitrogen mixed in the shielding gas.

6 tride, at least part of which is deposited as a fine solid phase due to the heat of the weld for producing a high notch-toughness weld.

2. A method as claimed in claim 1 in which the nitride producing metal is a metal taken from the group consisting of aluminum, titanium, zirconium, beryllium, columbium, vanadium and alloys thereof.

' 3. A method as claimed in claim 1 in which the step of supplying nitrogen to the weld comprises feeding nitrogen with the shielding gas.

4. A method as claimed in claim 1 in which the step of supplying nitrogen to the weld comprises providing a material which produces nitrogen when heated in the core rod used in the arc Welding.

5. A method as claimed in claim 4 in which the nitrogen Table 5 .Mechanical properties of multi-laye'r welds formed with an argon-nitrogen shielded arc Ordinary argon shielded are.

EXAMPLE 4 A core wire was prepared by charging a hollow core wire, with an outside diameter of 3.2 mm. and formed by bending a very soft steel sheet, with a powder prepared by mixing 0.5% aluminum, 0.3% titanium and manganese nitride in an amount suificient to produce enough nitrogen to form nitrides of the aluminum and titanium, together producing material is a material taken from the group consisting a manganese nit-ride, calcium nitride, molybdenum nitride, chromium nitride, and nitrates.

6. A method of arc welding high tensile strength steels and low temperature tough steels having high notchtoughness by depositing weld materials and using a gasshielded arc, comprising .the steps of using a core wire having a nitride producing metal therein in excess of the Welding materials that are normally present, and supplying a shielding gas which contains nitrogen to the arc, whereby the nitrogen combines with the nitride producing metal to form a nitride, at least part of which is deposited as a fine solid phase due to the heat of the weld for producing a high notch-toughness weld.

Table 6.Chemcal compositions (by percentages) and mechanical properties of welds formed by using a specially made hollow core wire 0 Si Mn Al Ti AlN TiN Fe Single layer weld 0. 08 0. 35 1. 27 0. 13 0. 06 0. 037 0. 062 Rem. Multi-layer Weld.-- 0. l1 0. 42 1. 36 0. 22 0. l0 0. 032 0. 068 Ram.

Tensile Yield Elonga- Impact value (Kg-mJcmfl) strength in point in tion in Drawing kg./mm. kg./mm. percent in percent 0. 0 C. Tr 15 Single layer weld--- 63. 5 54. 7 30. 2 60. 4 7. 6 17. 4 60 Multilayer we1d 67. 2 59. 1 28. 5 58. 2 5. 4 18. 3 -60 It is thus seen that the same effect as is produced in Examples 1 and 2 is produced with a carbon dioxide shielded arc and a hollow core wire containing nitrideproducing elements and a nitrogen producing compound.

What is claimed is:

1. A method of arc welding high tensile strength steels and low temperature tough steels having high notchtoughness by depositing weld materials and using a gasshielded arc, comprising the steps of supplying a nitride producing metal to the weld in excess of the welding materials that are normally present, and supplying nitrogen to the weld during the welding, whereby the nitrogen 7. A method as claimed in claim 6 in which the core wire contains 0.55% aluminum.

8. A method as claimed in claim 6 in which the core wire contains 0.52% titanium.

9. A method as claimed in claim 6 in which the core wire contains 0.34% aluminum and 0.23% titanium.

10. A method of arc welding high tensile strength steels and low temperature tough steels having high notchtoughness by depositing weld materials and using a gasshielded arc, comprising the steps of using a hollow core wire having a powder therein comprising aluminum and titanium and manganese nitride in an amount suflicient combines with the nitride producing metal to form a nito produce enough nitrogen to form nitrides of the aluminum and titanium, said core wire being used in addition to the filler materials that are normally used, and supplying a nitrogen free gas to the arc, whereby the nitrogen produced when the manganese nitride is heated combines with the nitride producing metals to form nitrides, at least part of which are deposited as a fine solid phase due to the heat of the weld for producing a high notch-toughness weld.

11. A core wire for use'in a gas-shielded arc welding method consisting essentially of 0.15% C, 0.368% Si, 1.34% Mn, 0.035% P, 0.24% S, 0.194% Cu, 0.55% Al, and remainder Fe, said percentages being by weight.

12, A core wire for use in a gas-shielded arc welding method consisting essentially of 0.13%, C, 0.364% Si, 1.32% Mn, 0.034% P, 0.024% S, 0.215% Cu, 0.52% Ti, and remainder Fe, said percentages being by weight.

13. A core wire for use in a gas-shielded arc welding method consisting essentially of 0.12% C, 0.68% Si, 1.80% Mn, 0.010% P, 0.007% S, 0.150% Cu, 0.34% Al, 0.23% Ti, and remainder Fe, said percentages being by weight.

14. A core wire for use in a gas-shielded arc welding method, said core wire having a nitride producing metal 8 therein taken from the group consisting of aluminum, titanium, zirconium, berrylium, columbium, vanadium and alloys thereof and a material which produces nitrogen when heated, said material being a material takenfrom the group consisting of manganese nitride, calcium nitride, molybdenum nitride, chromium nitride, and nitrates.

References Cited by the Examiner UNITED STATES PATENTS 2,121,055 6/1938 Smith 6161. 2,973,428 2/1961 Pfeiiferetal "219-137 3,036,205 5/1962 Aida et al 219- 3,066,215 11/1962 Espy 219-74 OTHER REFERENCES Hansen: Constitution of Binary Alloys, McGraw-Hill, 2nd ed., 1958, pages 935-937 relied on.

WHITMORE A. WHILTZ, Primary Examiner. JOHN F. CAMPBELL Examiner.

P. M. COHEN,.Assistav1t Examiner. 

1. A METHOD OF ARC WELDING HIGH TENSILE STRENGTH STEELS AND LOW TEMPERATURE TOUGH STEELS HAVING HIGH NOTCHTOUGHNESS BY DEPOSITING WELD MATERIALS AND USING A GASSHIELDED ARC, COMPRISING THE STEPS OF SUPPLYING A NITRIDE PRODUCING METAL TO THE WELD IN EXCESS OF THE WELDING MATERIALS THAT ARE NORMALLY PRESENT, AND SUPPLYING NITROGEN TO THE WELD DURING THE WELDING, WHEREBY THE NITROGEN COMBINES WITH THE NITRIDE PRODUCING METAL TO FORM A NITRIDE, AT LEAST PART OF WHICH IS DEPOSITED AS A FINE SOLID PHASE DUE TO THE HEAT OF THE WELD FOR PRODUCING A HIGH NOTCH-TOUGHNESS WELD. 